exec: support stdin fd being closed

Don't try to dup2() a file descriptor that is already
correct. This can happen if, for example, stdin is closed
and exec redirects stdin from a file, thus opening the input
as file descriptor 0.

Fixes #201

Signed-off-by: Steve Bennett <steveb@workware.net.au>

1 files changed, 3 insertions, 3 deletions

diff --git a/jim-exec.c b/jim-exec.c
index 5a21a1f..22bbdb8 100644
--- a/jim-exec.c
+++ b/jim-exec.c
@@ -1046,17 +1046,17 @@ badargs:
         if (pid == 0) {
             /* Child */
             /* Set up stdin, stdout, stderr */
-            if (inputId != -1) {
+            if (inputId != -1 && inputId != fileno(stdin)) {
                 dup2(inputId, fileno(stdin));
                 close(inputId);
             }
-            if (outputId != -1) {
+            if (outputId != -1 && outputId != fileno(stdout)) {
                 dup2(outputId, fileno(stdout));
                 if (outputId != errorId) {
                     close(outputId);
                 }
             }
-            if (errorId != -1) {
+            if (errorId != -1 && errorId != fileno(stderr)) {
                 dup2(errorId, fileno(stderr));
                 close(errorId);
             }